| 摘要 |
PURPOSE:To enable to receive a voice signal in multiplex, by providing the frequency conversion circuit, audio FM demodulation circuit, and audio signal system circuit including the de-emphasis circuit and audio adaptor circuit. CONSTITUTION:The FM audio IF signal fed to the video audio input terminal 8 is amplified 23 and converted into audio signal in VHF band after being fed to the frequency conversion circuit 20, and it is synthesized 21 with the video signal. In the multiplex of audio signal in this audio signal system, since it is converted into VHF TV signal without deteriorated characteristics, the audio multiplex broadcast can be received by connecting the output terminal 22 to the audio multiplex receiver. The audio multiplex signal is demodulated at the audio FM demodulation circuit 24 to be output at the audio multiplex output terminal 25. The de-emphasis circuit 13 is connected to the terminal 25 for the attenuation of the audio multiplex subchannel signal and the correction of the amplitude characteristics of the main channel audio. By connecting the input terminal 28 of the audio multiplex adaptor 29 to the terminal 25, the signal of main and subchannel signal is picked up in case of reception of multiplex broadcast. |
